JPH0195003A - Ceramic casting mold - Google Patents

Abstract

PURPOSE:To obtain a ceramic casting mold having no occurrence of cracks, high strength and excellent durability by making the mold with the material in which ceramic fiber is added to the material for a porous mold. CONSTITUTION:A ceramic casting mold is composed of the material in which ceramic fiber is added to the material for a porous mold. As the material for a porous mold, plaster or foamable acrylic resin, etc. is used. Ceramic fiber is mixed with the material for a porous mold in uniformly dispersed condition. As this ceramic fiber, glass fiber is suitable. For instance, in the ratio of water/ plaster, the material in which 1% of glass fiber 4 is added to 69% of plaster 3, is used. This plaster is poured into a metallic mold, and the plaster body taken out from the metallic mold is dried, whereby the plaster mold (a split mold composed of a top force 1 and a bottom force 2) for casting a disk, is produced. When the sludge of silicon nitride is cast into this plaster mold at 4kg/cm<2> of casting pressure, the plaster mold is not broken and the excellent molded object of silicon nitride may be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a mold used for casting of a ceramic material.

(Prior Art) The slip casting method, that is, the mud molding method is a traditional method for molding ceramics, but recently its importance has been newly recognized as a method for molding fine ceramics.

This molding method involves dispersing ceramic powder in a solvent to create a slurry, which is then cast into a mold made of a porous molding material such as water-absorbing plaster.The molding method uses relatively simple equipment and is complex. It is characterized by being able to form shaped objects and large-sized objects at low cost.

In this ceramic casting method, a gypsum mold generally made of gypsum is widely used as the mold. This is because plaster molds are easy to manufacture and have low manufacturing and material costs.

(Problem to be solved by the invention) However, although plaster molds have been used for a long time, cracks have occurred in the plaster molds due to the increase in the number of molded products produced by the casting method and the diversification of technology. Ceramic slurry often leaks from the plaster mold to the outside, which has become a problem. That is, as production volume increases, plaster molds are used more frequently, and as a result, plaster molds fatigue faster and cracks are more likely to occur. Also,
Recently, split molds have been widely used in casting molds, but when a split plaster mold is tightened from the outside with a clamp to secure the plaster mold, the clamping force can cause the plaster mold to crack. There are many.

Furthermore, in recent years, pressurized (depressurized) casting has been widely adopted to improve the density and strength of molded bodies. Plaster molds often crack when added.

Therefore, there is a demand for the development of a high-strength plaster mold that does not cause such cracks.

The present invention solves the above-mentioned problems, and aims to provide a ceramic casting mold with high strength and no cracking.

[Structure of the Invention] (Means and Effects for Solving the Problems) The inventor of the present invention has conducted various studies on molds used for ceramic casting, and has developed reinforcing parts to give strength to plaster molds. Mechanical structural methods have been adopted, such as reinforcing the plaster mold using molds, but in these cases the strength of the plaster mold cannot be improved as much as expected, and the structure of the mold becomes complicated and costs increase. There were drawbacks.

Therefore, as a result of further research, the inventor focused on the fact that the reason why gypsum cracks easily is because the bonds between the particles that make up gypsum are weak and the gypsum is brittle.When M-fibers are dispersed and mixed into gypsum, It was discovered that this fiber acts as a core material and suppresses the separation of particles from each other, thereby overcoming the brittleness of gypsum and increasing its strength. Furthermore, we discovered that ceramic fibers are the most suitable fiber material to be mixed into the plaster mold.

The present invention has been made based on this knowledge.

That is, the ceramic casting mold of the present invention is characterized in that it is formed of a material obtained by adding ceramic IIN to a porous mold material.

The ceramic mold of the present invention is formed using a porous mold material as the main material. Examples of the porous mold material include gypsum and foamable acrylic resin. Among these, gypsum is most suitable as a mold material because it is inexpensive and easy to manufacture molds.

Ceramic I-stripes are mixed in the porous mold material in a uniformly dispersed manner. As this ceramic mm, glass m
A cloth is suitable. Due to its m-string shape, glass fibers are entangled with the particles of the porous mold material and are very effective in reliably suppressing separation of the particles from each other. The reason for using ceramic fiber as Il navy added to porous mold material is
This is because it blends well with plaster mud, has good moldability, has high strength, and furthermore, does not cause a decrease in strength due to repeated drying of the plaster mold.

When mixing ceramic fibers into porous mold material,
without sacrificing the inherent water absorption properties of porous mold materials.
In addition, in order to increase the strength of porous mold materials without reducing the formability of the porous mold material when manufacturing molds, it is necessary to appropriately set the length and amount of ceramic fibers mixed in. be. Specifically, ceramics IJ
& miscellaneous lengths range from 0.5II1m to 5+nm, and ceramics mixed into the porous mold material! The amount of contaminants is 12% or less.

The inventor conducted the experiment described below to investigate the length and mixing ratio of ceramic fibers.

Glass fibers with fiber lengths of 0.5 mm, 3 mm, 5 mm, and 10 mm were added at a water/gypsum ratio of 0.69.
After drying the test pieces at a temperature of 50° C. for 15 hours, a bending test was performed on each test piece. The results of this test are shown in FIG. According to this diagram, the glass fiber length is Q, 5n
Below ++n, there is no noticeable improvement in the strength of the plaster;
When the glass fiber length exceeded 5 mm, no improvement in strength commensurate with the fiber length was observed in the plaster. Therefore, the fiber length of the ceramic fibers added to the porous mold material is 0.
．． 5-5. It can be seen that the range of Qmm is appropriate.

Next, the weight ratio of 11 glass fibers with an average length of 3n+m is 0.5.
%, 1%, 3%, and 5% water, and gypsum with a gypsum ratio of 0.69 were used to prepare test pieces, respectively, and these test pieces were dried at a temperature of 50°C for 15 hours. After that, a bending test was performed on each test piece. The results are shown in the diagram of FIG. According to this diagram, it is glass! There is a tendency for the bending strength of gypsum to increase as the addition amount of 1 m increases. However, when the amount added exceeds 12%, the increase in the strength of the gypsum reaches saturation, and moreover, the gypsum becomes unable to be uniformly dispersed, which impedes the water absorption of the gypsum. Therefore, it is appropriate that the proportion of ceramic [1 added to the porous mold material is 12% or less.

The ceramic casting mold of the present invention uses a material in which ceramic fibers are added to the porous mold material described above,
This material is made into a slurry by adding water and poured into a mold to produce a mold with a predetermined shape. This mold is a normal type,
It can be applied to a variety of things such as split molds and molds used in pressure casting methods.

Therefore, since the ceramic casting mold of the present invention is made of a porous molding material such as plaster mixed with ceramic fibers evenly dispersed, the ceramics am acts as a core material and becomes porous. The particles of the mold material are tightly connected and do not separate easily, eliminating brittleness and having sufficient mechanical strength. Therefore, the mold of the present invention, such as a plaster mold, will not break even if it is used frequently.

Furthermore, if the mold is a split mold, the mold will not be damaged by the clamping force due to the clamp. Furthermore, when casting is performed using the pressure casting method, the mold does not crack due to the casting pressure. Therefore, this ceramic mold has excellent durability.

(Example) An embodiment of the present invention will be described with reference to the drawings.

The material used is 1% of gypsum with a water/gypsum ratio of 69 and 111 ft of glass with a fiber length of 3 alIl.

Then, this plaster was poured into a mold, and the plaster body taken out from the mold was dried at a temperature of 60°C for 15 hours.
As shown in the figure, a plaster mold (a split mold consisting of an upper mold 1 and a lower mold 2) for casting a disc with a diameter of 150 mm and a thickness of 1 Q mm was manufactured.

Note that in Figure 2, 3 is plaster and 4 is glass fiber. and,
Silicon nitride slurry was cast into this plaster mold at a casting pressure of 4/(y/ci).As a result, there was no damage to the plaster mold and a healthy silicon nitride molded body was obtained.Furthermore,
Although this casting molding was performed 20 times in succession, no damage to the plaster mold occurred.

[Effects of the Invention] As explained above, according to the present invention, it is possible to obtain a ceramic casting mold that is free from cracking, has high strength, and has excellent durability.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is a diagram showing the relationship between the bending strength of plaster and the fiber length of glass fibers, and Fig. 3 is a diagram showing the relationship between the bending strength of plaster and the fiber length of glass fibers. It is a diagram showing the relationship with the amount of addition. 3...Gypsum, 4...Glass fiber. Applicant's agent Patent attorney Takehiko Suzue Figure 1 0.5 3 5 10 Absolute loss (mm) Figure 2 OQ5 1 5 10 Amount of yarn weight (w t 01o) 30th

Claims (5)

[Claims] (1) A ceramic casting mold, characterized in that it is made of a porous molding material with ceramic fibers added thereto. (2) The first claim is that the porous mold material is gypsum.
Mold for ceramic casting described in Section 1. (3) The mold for ceramic casting according to claim 1, wherein the fibers have a length of 0.5 to 5 mm. (4) The mold for ceramic casting according to claim 1, wherein the amount of ceramic fiber added is 12% or less by weight. (5) The ceramic casting mold according to claim 1, wherein the ceramic fiber is glass fiber.